SYNTHESIS OF BIOLOGICALLY-INSPIRED NANOFILTRATION MEMBRANES USING PROTECTED, MUTATED, AND SIMULATED AQUAPORINS

Gram-negative bacterial cells are surrounded by a cell membrane which protects the cell and controls the transport of nutrients and waste products in and out of the cells at a fast rate. This rapid transport of nutrients and wastes through the cell membrane is made possible by channel proteins called porins. Various types of porins present in the cell membrane have specific functions depending on their selectivity towards different nutrients, and channel proteins selective towards water are called aquaporins. These proteins restrict the passage of all entities except water molecules and they provide a fast transport rate of water molecules at 109 molecules/second per channel. The high selectivity of porins has led to their incorporation into synthetic systems, and one example is the addition of porins to separations membranes in order to enhance their performance in terms of selectivity and permeability, in a field called biomimetics. The concept of incorporating aquaporins into synthetic membranes has been studied for the last 10 years in order to enhance the water permeability and selectivity of membranes for water purification; however, there are still limitations such as high costs, difficulties in fabrication of aquaporins, their alignment into synthetic membrane assembly, low stability, and limitations on number of aquaporin molecules that can be introduced into synthetic membranes limit their applicability. In recent years, concurrent with the work on aquaporin-based biomimetic membranes, there has been an increase in the study of synthesizing molecules with similar structure-function relationships of aquaporins. These artificial channels attempt to mimic the high-water permeability and selectivity of aquaporins, while being synthesized using simple chemistry, being solvent compatible, and requiring less space on the membrane surface which helps to incorporate more channels into the membrane assembly. The objectives of this study were to first incorporate aquaporins into synthetic nanofiltration membranes without chemical alteration them to prevent flattening or denaturing of aquaporins; then, the second objective was to install functional groups on aquaporins and align them in the direction of water flow; lastly, the third objective was to synthesize artificial channels in order to overcome the issues with aquaporin stability, alignment, and efficient packing of water channels onto the membrane surface. For the first objective, aquaporins were treated with a polysaccharide, gum Arabic, and incorporated into an amphiphilic polymer, polyvinyl alcohol with alkyl side chains (PVA-alkyl), in order to simulate the natural housing of lipid bilayer for aquaporins and to protect them from denaturing. Long alkyl chains provided the hydrophobic component, while PVA provided the hydrophilic component of the amphiphilic polymer. Membranes modified with aquaporins displayed lower flux declines and higher flux recoveries after reverse flow filtration, along with improved rejection values for both protein and salt solutions as compared to PBI and PBI-PVA-alkyl membranes. However, there was leakage of ions between channels. Therefore, in order to improve the rejection of protons, ions and other impurities, the channels were aligned with the direction of water flow. Functional groups were installed on Aquaporins using site-directed mutagenesis for covalent attachment to the polymer matrix so that the proteins could be immobilized to the membranes and aligned in the direction of the flow. Aquaporin constructs were modified to bear affinity tags or unique amino acids at the N-terminus of the aquaporin molecule, which was used to facilitate directional immobilization. Each aquaporin monomer was modified with a unique amino acid Cys group at the N-terminus right after the first Met, and due to the aquaporin tetrameric nature, these Cys groups became four anchors for attachment. The presence of these four Cys anchors per aquaporin tetramer was used to attach on the membrane surface in alignment with the feed water flow direction. Membranes modified with mutated aquaporins showed consistently higher salt rejection values of ~70% irrespective of feed concentration, along with higher flux recoveries and lower flux declines. Commercial NF-270 membranes provide a monovalent salt (NaCl) rejection of ~50% and divalent salt (MgCl2) rejection of 97%. Also, approximate coverage of membrane surface with attached aquaporins was calculated using simulation studies. Simulation studies showed that immobilized aquaporins with PVA-alkyl provided a diffusion rate equivalent to 64% coverage on the membrane surface. This showed that aquaporins didn’t cover the entire surface area of the membrane. However, immobilized aquaporins were responsible for the rejection of a portion of ions passing through the membrane. In order to overcome the limitations of aquaporin incorporation into polymer membranes, artificial organic frameworks were added as surface modification on PBI membranes. Organic frameworks were synthesized as derivatives of hybrid bisamides. The series of bisamides 1-4 consist of 6-amino-pyridine-2-dicarboxylic acid, 6-hydroxymethyl-pyridine-2-carboxylic acid and ethylenediamine, trimethylenediamine, putrescine, and cadaverine depending on the length of carbon chain. These frameworks are amphiphilic in nature and have strong chemical attachment due to the presence of amines and carboxylic acids into each building block. These molecules were introduced into the membrane matrix using carbodiimide chemistry. FTIR results showed the attachment of these bisamide molecules onto the surface of a modified PBI membrane. Also, modified membranes showed a reduced molecular weight cut off (MWCO) for neutral organic molecules. Overall, membranes modified with aquaporins have shown a potential to provide consistently high salt rejections with increasing feed solutions. Also, preliminary results have shown that bisamide molecules can be attached onto the membrane surface as organic frameworks and have a potential to be an alternative for aquaporins based biomimetic membranes

Anioonide retseptorid: Süntees ja seondumise täppismõõtmised

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Käesoleva doktoritöö teemaks on erinevate anioone siduvate molekulaarretseptorite süntees ning uudse kõrge täpsusega NMR-põhise mõõtemetoodika väljatöötamine seondumistasakaalude uurimiseks. Sünteesitud retseptorid kasutavad sidumistsentritena uurea, tiouurea, karbasooli, indooli ja indolokarbasooli fragmente ning nende kombinatsioone. Suhtelise seondumisaktiivsuse mõõtmine absoluutse asemel annab võimaluse saada kõrge usaldusväärsusega tulemusi, kuna paljud määramatuse allikad – näiteks ioonpaardumine ja homokonjugatsioon – taanduvad välja. Meetodit rakendati 38 sünteetilise retseptori ja nelja karboksülaataniooni – laktaat, bensoaat, atsetaat, trimetüülatsetaat – vahelise seondumise uurimisele 0.5% H2O lisandiga DMSO-d6 keskkonnas. Saadi suurepärase kooskõlalisusega (0.01 log ühikut) skaalad. Saadud tulemused näitavad, et seondumisaktiivsuse olulisim anioonipoolne mõjutaja on aniooni aluselisus. Seondumisafiinsus kasvab aniooni aluselisuse kasvuga: laktaat < bensoaat < atsetaat trimetüülatsetaat. Siiski, mitmetel juhtudel esineb seondumisjärjekorra muutuseid, iseäranis atsetaadi ja trimetüülatsetaadi korral. Loodud NMR-põhise seondumisafiinsuse mõõtemeetodi rakendatavus ja eelised leidsid kinnitust: puudub vajadus mõõta aniooni või retseptori kontsentratsiooni, kõrge täpsus ja usaldusväärsus, võimalus detekteerida retseptori deprotoneerumist, võimalus mõõta kuni kuus retseptorit samas lahuses.The current dissertation focused on synthesis of different types of molecular receptors for anions, based on different binding moieties, such as urea, thiourea, carbazole, indole, indolocarbazole, as well as their combinations and on development of a novel accurate NMR-based binding affinity measurement method using the relative binding approach. Measuring the relative binding affinity instead of absolute binding affinity it is possible to obtain highly accurate result because many sources of uncertainty such as ion-pairing and homoconjugation cancel out. The method was applied to the measurement of 38 synthetic receptors towards lactate, benzoate, acetate and trimethylacetate anions in 0.5% H2O:DMSO-d6 with excellent consistency parameters around 0.01. The results indicate that on the anion side the binding affinity is largely determined by the anion basicity, higher is the anion basicity, stronger is the binding. The binding affinity orders increasing from lactate benzoate acetate trimethylacetate. Nevertheless, there are a number of occasion binding affinity order changes with changing the carboxylate anions, especially in the case of acetate and trimethylacetate anions. The applicability and advantages of the NMR method for measuring the relative binding affinity have been demonstrated: no need to measure the activity of anion and receptor concentration, high accuracy, robust, possible to see the receptor deprotonation and possible to measure up to six receptors in one solution

Is Attentional Channel Processing Design Required? Comprehensive Analysis Of Robustness Between Vision Transformers And Fully Attentional Networks

The robustness testing has been performed for standard CNN models and Vision Transformers, however there is a lack of comprehensive study between the robustness of traditional Vision Transformers without an extra attentional channel design and the latest fully attentional network(FAN) models. So in this paper, we use the ImageNet dataset to compare the robustness of fully attentional network(FAN) models with traditional Vision Transformers to understand the role of an attentional channel processing design using white box attacks and also study the transferability between the same using black box attacks.Comment: 4 pages, 12 figure

A Review: Data Mining Technique Used for Searching the Keywords

Convential Spatial queries contains range search, nearest neighbor retrival involve only conditions on object geometric properties. Today, many modern applications call for innovative kind of queries that aim to find objects satisfying both a spatial predicate, and a predicate on their associated texts. For example, instead of considering all the restaurants, a nearest neighbor query would instead ask for the restaurant that is the closest among those whose menus contain “Dosa, Idli, Wadapav” all at the same time. Currently the best solution to such queries is based on the IR2-tree, which, such type of queries can be efficiently handled by IR2tree. In the proposed work, we are developing a system searching is done on the basis of methods like nearest neighbor search with keywords is done by IR2 tree and spatial inverted index.We could first fetch all the restaurants whose menus contain the set of keywords {Dosa, Idli, Wadapav}, and then from the retrieved restaurants, find the nearest one The IR2-tree combines the R tree with signature files. Inverted indexes (I-index) have proved to be an effective access method for keyword based document retrieval

Endoscopic Management of Leaks and Fistula in Gastrointestinal Tract

Leak, perforation, and fistula are the three main types of transmural defects in the gastrointestinal (GI) tract. Evolution of interventional endoscopic\ techniques as well as widespread use of laparoscopic and bariatric surgical procedures has contributed to the rising incidence of GI defects. The basic principle for management of leaks and fistula is to provide a barricade to the flow of luminal contents across the defect. This can be achieved either by a surgical or endoscopic method. Minimally invasive closure techniques such as clipping, stenting, suturing, and endoscopic vacuum therapy have revolutionized the management of GI defects. This chapter deals with endoscopic techniques and their present status in the management of luminal GI leaks and fistula

Formulation and In-Vitro Evaluation of Buclizine Buccoadhesive Tablets

Buclizine is an antihistamine that is used to treat motions sickness, especially to prevent and treat symptoms such as abdominal pain, dizziness, nausea, vomiting, headaches, etc. It may also be used either alone or in a combination with other medicines for the treatment of hay fever and other allergic conditions. These dosages form make close contact with buccal mucosa, avoid first- pass metabolism, increase absorption and patient compliance, results in an enhanced drug bioavailability. Buccal adhesive tablets were prepared by direct compression. Carbopol 940 and Sodium Alginate was used in different ratios and also in combination. Formulated 10 batches were evaluated for physical parameter, swelling studies, bioadhesion studies, and in-vitro drug release and in-vitro drug permeation. Bioadhesion studies were carried out to determine mucoadhesive potential of prepared tablets. Tablets were evaluated for in-vitro drug release for 6 hrs, using USP type II method and. From these results it can be concluded that formulation batch F6 was most promising comprising of 1:4 ratio of Sodium Alginate. The best fit model for the optimized batch F6 was zero order having R value 0.9889 and K value is 0.2542. &nbsp;Keywords: Buclizine, Carbopol 940, Sodium Alginate, buccal tablet, in-vitro drug permeatio

Review on Optical Character Recognition of Devanagari Script Using Neural Network

During the last decades lot of research work has been done in the field of character recognition on various scripts in various languages. In India peoples are used to speak national language Hindi and spoken by more than 500 million people. Many languages in India, such as Hindi, Marathi and Sanskrit has uses Devanagari as its base script .As compared to English character; Indian script (Devanagri) characters are complicated for recognition. Devnagri script is the basis for many Indian script including Hindi, Sanskrit, Marathi, Kashmiri, and so on. In this paper we present a review of research work that has been done in the field of character recognition in Devanagari script in past

Feature Extraction Techniques for Marathi Character Classification using Neural Networks Models

Hand written Marathi Character Recognition is challenges to the researchers due to the complex structure. This paper presents a novel approach for recognition of unconstrained handwritten Marathi characters. The recognition is carried out using multiple feature extraction methods and classification scheme. The initial stages of feature extraction are based upon the pixel value features and the classification of the characters is done according to the structural parameters into 44 classes. The final stage of feature extraction makes use of the zoning features. First Pixel values are used as features and these values are further modified as another set of features. All these features are then applied to neural network for recognition. A separate neural network is built for each type of feature. The average recognition rate is found to be 67.96% , 82.67%,63,46% and 76.46% respectively for feed forward , radial basis , elman and pattern recognition neural networks for handwritten marathi characters

Performance analysis of Handwritten Devnagari Character Recognition using Feed Forward , Radial Basis , Elman Back Propagation, and Pattern Recognition Neural Network Model Using Different Feature Extraction Methods

This paper describes the performance analysis for the four types of neural network with different feature extraction methods for character recognition of hand written devnagari alphabets. We have implemented four types of networks i.e. Feed forward , Radial basis, Elman back propagation and Pattern recognition neural network using three different types of feature extraction methods i.e. pixel value, histogram and blocks mean for each network. These algorithms have been performed better than the conventional approaches of neural network for pattern recognition. It has been analyzed that the Radial Basis neural network performs better compared to other types of networks